Lag from 2000-3000 RPM/Bad coil pack or boost control solenoid?

I have been having an issue with my '05 LGT where it sputters and seems to lag from about 2000 RPM to 3000 RPM until the turbo spools up and it starts to pull. I'm thinking that it is either a bad coil pack or boost control solenoid. There are no codes at all. I do not have a boost gauge so I don't know what it's pushing for PSI throughout that time. Does anyone have any thoughts or suggestions on it?

Clean the MAF sensor first, auto parts stores have a can of MAF cleaner.

Is the air filter clean ?

How do you go about cleaning the MAF? The air filter isn't spotless but it isn't completely clogged. I'm sure it is losing some air flow.

If I'm going to buy a new $50 K&N air filter though, I might as well spend another $200 for a cold air intake or short ram intake, right?

Boost control solenoids rarely go out and at 2,000 rpm it won't be doing anything. If cleaning the MAF and air filter doesn't work, it may be the passenger side cam position sensor. I just changed mine out because of the same problem.

 

My '06 spec. B. just cracked 265,000 miles. Seals, sensors, gaskets and hoses in the corner of the engine near the turbo have either been replaced or I keep a close eye on them. The passenger side cam position sensor is tucked in on the top of the head in front of the turbo. It pops out with a single 10mm.

 

-Clif

Do not buy a cold air intake. the car comes with one that is hard to beat.

 

The MAF is right on top of the hose off the intake air filter box, two screws and it comes out. spray up the tube with the cleaner and let it dry for a few minutes.

 

The IAT is the probe off the side of the MAF

How do you go about cleaning the MAF? The air filter isn't spotless but it isn't completely clogged. I'm sure it is losing some air flow.

If I'm going to buy a new $50 K&N air filter though, I might as well spend another $200 for a cold air intake or short ram intake, right?

 

Anything intake you change before you're producing 400hp is a waste of money. If you change your intake anyway you need a new tune.

Now is that something that would go early on? I have almost 121,000. Is it hit or miss when those will go or is it a benchmark like the 100k line?

 

As far as cleaning the MAF goes, I'll be sure to go buy the cleaner ASAP and give that a try and also pick up a new air filter.

 

I appreciate the help, guys

maclif's post really makes good sense to me. Especially on higher mileage cars, those sensors get cooked.

 

Be sure to post up your results after you clean your MAF!

just cracked 265,000 miles.

-Clif

 

:eek:

When my cam sensor started going out it would run pretty decent most of the time. It generally felt like an engine running rich. But there would be intermittent times when the boost would hit like normal but the car would not get out of it's own way until it hit around 3,800 rpm.

 

I've got a great relationship with two of the most senior Subaru mechanics in Dallas (comes with driving four Subarus a total of around a half a million miles). I talked with one of them and he confirmed that's what the motors act like when a cam sensor is on it's way out.

 

In less than a month, I swapped out the cam sensor and front 02 sensor. Car drives distinctly better and my highway fuel economy went up pretty dramatically. According to my calculations, the two new sensors will pay for themselves in fuel savings in about 8,000 miles. You know, two months give or take.

 

-Clif

Sorry to Threadjack, but does the Cam Position Sensor not throw a CEL? I have a similar problem and my 05 LGT has almost 130,000 on the motor. I was told the tune causes hesitation as well, but I want to be relatively sure that that is the issue before I spend $500+ on a COBB AP.

I do not know if the cam sensor reaches a point where it will throw a CEL, but I have experienced a state of partial failure which did not throw a CEL. Replacing the cam sensor, as recommended by a tech I trust solved the problem.

 

-Clif

I apologize for the delayed response with results! I have been busy this week. I took a trip up to AutoZone this morning and purchased a can of MAF cleaner and a new K&N panel filter and she runs great! No hesitation, no falling on its' face, nothing. The car hasn't run this good since I bought it! Thank you all for the input and help. I appreciate it.

 

-Richie

Incredibly happy to find this post; my 05 GT is currently having the exact same problem. Lag or jerkiness throughout 2k-3k RPM, past that it feels like the turbo finally kicks on and runs smooth. For me it's especially noticeable starting from a stop while going up hills.

 

Going to try the MAF cleaner and new filter as well. I'll post back.

 

Update: Cleaning MAF and replacing the filter did nothing Since then I've had it in the shop, gotten the fuel intake lines replaced, and O2 sensor replaced. Jerkiness is still present. The mechanic said that what I'm feeling is normal, which I just can't imagine some one test driving this thing and being like "YEAH SIGN ME UP FOR THIS JERKY RIDE!" But on the plus side, I've had about 5 grand worth of work done on this thing so far and it's only cost me about 400 bucks because of the warranty I got from Carmax. The only warranty I've ever had that's been worth it's salt.

It worked great for me! I put a new K&N panel filter in, cleaned the MAF and it ran/runs like a champ! I couldn't believe how easy the fix was.

It worked great for me! I put a new K&N panel filter in, cleaned the MAF and it ran/runs like a champ! I couldn't believe how easy the fix was.

 

 

Did you reset the ECU afterwards? And do you have a tune to run that panel filter?

The issue with teh K&N is the oil wicks and gums up the MAF. Best is to just use the stock paper filter and ditch them when dirty.

 

If you must run one it is a good suggestion to make sure the tune is modified for it in place.

 

I pulled my K&N after fighting to keep the MAF clean...

 

OCVS is also another item that the car would benifit from replacing. It really should be on the 105K schedule.

 

As for the Cam sensor I had let my wife drive down to San Diego with the car and she called in limp mode on the other side of the grape vine (hwy 5).

 

Luckely I left the AP in the car and walked her and the boy through the CEL ID and clear. Didn't come back after and I replaced the cam sensors ASAP.

 

146K and now going strong with a new turbo and etune from Cryo.

Where is the Cam sensor that you guys are talking about?

DING! I am having similar issues. Does the cam sensor throw a CEL? I believe their is only one cam sensor on 05LGT located on the driver side - or am I wrong?

I've heard that this is an issue with 05's and that Subaru was able to get rid of it by the 07's. I have also heard that it might be possible to tune it out with enough work but I'm in Machinenoise's position, replaced just about every damn thing in the car and it's still there. I'll try to get a video of the tach when it's doing it because you can see it jumping up and down until you get to just past 3k RPM.

how are the OCV's? if you have logging capabilities log VVT advance left and right and see if they are in sync. If not, replace those. I was getting some really bad stumbling at low RPM and new valves seem to have cleared it up.

OCVS was the big part that solved the stumbles for me. Mine was stalling ro having a conniption fit at idle and just off idle conditions. In parking lots or bumper to bumper traffic. On the pipe no stumble.

 

Glad I bumped back int this thread cause I want to replace my crank sensor for good measure on this next rebuild.

and you've eliminated things like knock and boost/vacuum leaks? I have a intermittent false knock that chokes out the timing.

So, I replaced both Cam sensors, and the problem one was not the passenger side next to the turbo, as originally thought, but was the driver-side. Go figure. BUT, the hesitation is GONE! I'm going to clean the OCV's next week and inspect for anything fishy with them to be safe - and if need be replace them.

 

I really appreciate everyone's feedback. This is a great community!

 

These are for Furious George since he asked for the location. Unfortunately the driver-side sensor was buried under a lot of engine chaos and was installed blindly - so no pics.

 

Cam Sensor Passenger Side:

http://machinenoise.com/subaru/cam-sensor.jpg

Best just to change the OCVS if conditions like high mileage and hesitation are part of the equation. Since it's an electrical solinoid that is sealed off from the oil delivery cleaning will never fix this part. Best to replace altogether. IMO should be part of the 105K service.